38. Differential peroxidase isozyme patterns between radiation-induced dwarf mutants and their parent in rice.

Laboratory of Radiation Genetics and Chemical Mutagenesis, Faculty of Agriculture, University of Tokyo, Bunkyo-ku, Tokyo, 113 Japan

Peroxidases exist in a great variety of multiple forms in different organs and tissues of plants (Shannon 1969; Grison and Pilet 1985). We have compared peroxidase isozyme patterns between two radiation-induced dwarf mutants and their parental cultivar, and have found a difference in isozyme pattern from the stem tissues.

The induced semidwarf cultivar Reimei, a dwarf mutant line Fukei No. 71 and their original cultivar Fujiminori were compared, while the former two had been derived from Fujiminori after ⁶⁰Co gamma-exposure (Futsuhara 1968). The leaves, stems and roots were separated from plants grown for two months under natural conditions. The tissues of each organ were ground in 10 ml per g fresh weight of 50 mM Tris-HC1 buffer (pH 7.0) at 4 degrees C. Then, the homogenate was centrifuged at 20,000 X g for 20 min. at 4 degrees C. The supernatant contained 30 ug proteins when measured by the method of Lowry (1951). It was used for iso-electric focusing electrophoresis with disk polyacrylamide gel (5.25%) containing Ampholine (pH 3.5-10 LKB). Electrophoresis was performed at 200V for the first 14 hours, followed by 400V for the last one hour. After electrophoresis, the electrofocused gel was stained with the reacting mixture containing 0.1% odianisidine, 0.03% hydrogen peroxide and 0.06M acetate buffer (pH 4.9) at 4 degrees C.

Fig. 1 shows the peroxidase zymograms in the leaves (panel A), roots (panel B) and stems (panel C) of plants grown for two months under natural conditions. In the leaves and roots, Fujiminori, Reimei and Fukei No. 71 showed the same band pattern. In the stems, however, the three strains showed differential patterns, as indicated by arrowheads in Fig. 1.

The zymograms observed in different tissues of these normal, semidwarf and dwarf plants are schematically depicted in Fig. 2. Differences were deteected only in the zymograms of stem tissues as to the three bands at pI 8.3 (band No. 9), pI 8.4 (band No. 11) and pI 8.5 (band No. 12). Band No. 9 in Fujiminori, No. 11 in Reimei, and No. 12 in Fukei No. 71 were observed with a particularly high intensity.

On the other hand, bands No. 5, 13, 14, 17 and some others were tissue- specific. Band No. 5 was present only in leaves and root. Bands No. 5 was present only in leaves and root. Bands No. 13 and 14 were absent in root. Bands No. 17 and 19 were absent in the leaves. However, no differences in these bands were found among the three strains.

Fujiminori, Reimei and Fukei No. 71 may be considered as isogenic lines differing only in induced dwarfing genes. The differences in peroxidases of stem tissues found among the three lines would reflect differential actions of those dwarfing genes.

Fig. 1. Zymograms of peroxidase isozyme in different tissues of rice plants grown for two months under natural conditions.

Fig. 2. Schematic representation of peroxidase isozyme patterns in several tissues of rice plants.

Futsuhara, Y., 1968. Breeding of a new rice variety Reimei by gamma-ray irradiation. Gamma Field Symp. 7: 87-109.

Grison, R. and P.E. Pilet, 1985. Cytoplasmic and wall isoperoxidases in growing maize roots. J. Plant Physiol. 118: 189-199.

Lowry, O.H., N.J. Rowebrough, L.A. Farr and R.J. Randall, 1951. Protein measurement with the Folin phenol reagent. J. Biol. Chem. 193: 265-275.